Stochastic-Based Reliability Analysis of Stainless-Steel Beams Under Bending

The presented article studies the bending resistance of a stainless steel hot-rolled profile UPE 80, which is stressed by bending around the minor principal axis. Resistance is studied as the random output variable, which is a function of input material and geometric characteristics. The paper deals with the stochastic analysis of this static resistance. The computational model is created on the basis of the finite element method using geometric and materially nonlinear solution. The Ansys software with 4-node Shell 181 element is used. The input random variables of the stainless steel are taken from previous research aimed at identifying the material mechanical properties based on experimental research of austenitic chromium-nickel stainless steel 1.4307/AISI 304 L. Statistical analysis is performed using the Latin Hypercube Sampling method. The probability of achieving standard design resistance is estimated and compared with the reliability level in standard EN1990 given by the reliability factor beta 3.8. The article discusses the need for a larger number of samples for reliable estimates of design resistances and for the verification of partial reliability factors, which are a challenge for further research.

Deformational behavior and damage mechanism of R-UHPFRC beam subjected to fatigue loading

The fatigue behavior of a reinforced UHPFRC (Ultra High Performance Fiber Reinforced Cementitious composite) T-shaped beam under four-point bending is investigated. The beam was subjected to a fatigue loading range equal to 49% of the static resistance and failed after 0.88 million cycles. It was instrumented with extensometers, strain gauges and distributed fiber optic sensors for strain monitoring. The fatigue process consists of three stages: with rapid, stable and again rapid growth of strains during 10%, 80% and 10% of total number of fatigue cycles, respectively. Except of the first 10%, this process takes place locally; therefore, it cannot be followed with the deflection measurement. During the stable stage, growth of strain occurs at minimum loading level in the fatigue cycle, indicating a fatigue damage process under tensile-compressive response of UHPFRC. Advanced fatigue crack propagation in the reinforcement bar determines the location of rupture of the beam. When the remaining cross-section of the rebar does not suffice to carry the tensile load, stress is transmitted to the encompassing UHPFRC causing its fast deterioration. Complete rupture of the rebar occurs only at the end of the test, when the beam collapses.

Dynamic driving formulas and static loadings in the light of wave equation solutions

The advances in pile monitoring have motivated attempts to support dynamic formulas to estimate pile bearing capacity. Based on numerical analysis of the wave equation and the results of dynamic loading tests in three piles the paper deals with the investigation of the soundness of some of the most used in Brazil, namely, the so called Chellis-Velloso Formula, the Energy Approach Equation and Uto’s Formula. The former gained strength through a misinterpretation of Casagrande (1942) statement that the elastic compression of a pile during driving is a measure of the dynamic force with which the soil is tested, and not of its static resistance. Therefore, the elastic compression and rebound, measured during driving, are generally smaller than the corresponding static values. The second is based on an elasto-plastic load-displacement relationship without physical meaning, besides the fact that the effective energy in driving a pile is related to the work of dynamic forces and has nothing to do with the static resistances. The third was derived from a simplified solution of the wave equation, assuming among other hypothesis that there is no friction along pile shaft. The paper shows the ineffectiveness of attempts to universally validate these formulas with dynamic pile monitoring and the implications in the simulation of static loadings.

Application of X-Ray Diffraction to Study Mineralogical Dependence of Reduction: Disintegration Indices RDI of Blast Furnace Sinters

The aim of this research was to continue an examination of influence of mineral components of blast furnace sinters on their quality. Two of reduction-disintegration indices RDI were taken into account: static resistance to degradation RDI-1+6.3 and static susceptibility to degradation RDI-1-3.15. X-ray diffraction was used for phase identification and the Rietveld method was applied to study quantitative dependence. Static susceptibility to degradation RDI-1-3.15 showed clearly dependence on quantitative mineral composition, namely on quantities of magnetite, silicates and slag phases. Static resistance to degradation RDI-1+6.3 was also dependent on fractions of magnetite and silicates.

Rules of Engagement in Minimal Blood Loss Palatoplasty Using Saline Hydro Dissection: A Useful Learning Curve for Younger Cleft Surgeons in Manoeuvring Areas of Static Resistance due to Tight Tissue Planes

Minimal blood loss in palatoplasty can be achieved with adrenaline saline hydro dissection, and a good knowledge of key anatomical structures as well as the stubborn areas of static resistance, where dissection is difficult because of fixed tissue planes. With the advent of minimal incision palatoplasty, button-hole and medial-only incision procedures, the amount of blood loss is significantly reduced in most palate operations. The two-stage palate repair also leads to less blood loss and is a popular concept among cleft groups worldwide following the initial promotion by Swedish cleft groups at Gothenburg. The learning curve is reasonable and techniques can be added, as one gains more experience with cleft palate surgeries.